Means for recording and reproducing sound



' L. DE FOREST MEANS FOR RECORDING AND REPRODUCING SOUND Original FiledSept. 18, 1919 m 0 OUWNTQR N Y ATToR i jgaM Patented Jan. 29, 1924.

UNITED STATES PATENT OFFICE.

LEE DE FOREST, OF NEW YORK, N. Y., ASSIGNOR T DE FOREST PHONOFTLMCORPORA- TION, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF DELAWARE.

MEANS FOR RECORDING AND REPRODUCING SOUND.

Original application filed September 18, 1919, Serial 1T0. 324,683.Patent No. 1,446,246, dated February 20,

' 1923. Divided and this application filed November 11, 1920. Serial No.423:276.

T 0 all whomz't may concern Be it known that I, Len on F'onns'r, acitizen of the United States, and a resident of New York, in the countyand State of New York, have invented a certain new and usefulImprovement in Means for Recording and Reproducing Sound, of which thefollowing is a specification.

This invention relates to making a record of sound waves suitable forreproduction from the record so made and is directed to thesubject-matter divided from my co-pending application U. S. Serial No.324,683,

filed September 18th, 1919, issued 'as Patent No. 1,446,246,'Feb-.20,1923.

The object-of the invention is to provide an electrically controlledmeans for recording sound. z y

. A. further obj ect of the invention is to pro- 20 videelectricallycontrolled means for photographically recording sound.

Further objects of the invention will appear more fully hereinafter.

The invention consists substantially in the construction, combinationlocation and relative arrangement of parts, together with the novelmethods employed in accordance therewith, all as will be more fullyherein- 3 after set forth, as shown by the accompanying drawings andfinally pointed out in the appended claims.

Referrin to the drawings The sing e figure illustrates a sound recordingarrangement embodying my invention.'

In my co-pending application from which the subject-matter of thispresent case is divided, I have shown and described means forrecordingsound waves upon a photographic film, such as an ordinary filmemployed in motion picture photography, and I have therein set forth andhave described that a source of'light may be directly controlled in theintensity, pitch and volume of sound in such; a manner that thefluctuations caused by sound waves in the intensity of light emittedfrom the source may be photographed upon the film. I

In accordance withv my present invention I employ a small arc lamp 552,preferably consisting of two heavy tungsten ball electrodes 50 and 51,separated by a small gap,

for example, 0.5 millimeter, mounted in the small vessel 52, eitherevacuatedor filled with some gas, such as nitrogen, mercury vapor, etc,to make the light from such are as rich as possible in ultra violetrays. The light rays from the arc lamp pass through the lens 3 in theusual well known manner and in addition thereto, if desired, through acolor filter 4, which color filter is preferably of a dark blue, as Ihave found that the best results of recording sound wavesphotographically are thus secured. A photographic film 7 is passed bythe lens and film 3 and 4 respectively in the usual well ktnowln mannerand the light emanating from the lamp is recorded on the film,preferably in the nature of a minute ray ob tained from a pin pointaperture or focused to a point by a lens. I energize the arc lamp 552'from a source of high frequency current, the frequency of which must bewell above the audible limits and modulate the high frequency currentssupplied the arc lamp with alternating or pulsating currents set up byand in accordance with sound waves. For example, but to which I do notdesire to be limited or restricted, the high frequency currents may besupplied to the arc lamp by oscillion is shown at and comprises theusual plate electrode 61 and grid electrode the oscillion systemillustrated, wherein the nected at its terminals to the respective ballsI 50 and 51 of the small arc lamp 52. Condensers 66 are shunted aroundthe inductance '64 and a tap connection 67 is provided between theoscillating circuit thus formed and the. filament electrode 63 includingtherein an impedance coil 68 and a source of current 69, preferablyshunted by a condenser 70. An impedance coil is likewise interposedbetween the source 69 and the filament electrode. The foregoing isbriefly a well-established and now a well-known form of high frequencygeneration circuit forming the subject-matter of separate patents andapplications. The alternating or pulsating currents produced by themicrophone 5, which is included in circuit with a current source 6 andone coil 17 of a transformer, the othercoil 18 of which is included inthe input circuit of an audion amplifier 90, and thus amplified aresupp-lied by the output circuit of the audion amplifier 90 to thetransformer coil 91 included therein, and thence to the transformer coil92 in cluded in the grid filament circuit of the oscillion 60, therebyeffecting a modulation of the high frequency oscillations generated bythe balance of the oscillion systems, and the modulated high frequencyoscillations vary the degree of brilliancy of light emitted fro-m theare light by the unmodulated high frequency currents, which variationsare proportional in every respect to the original modulating audiblefrequency alternating or pulsating currents in the microphone circuit.The application of the foregoing principles are many and while I haveshown and will now described its application to motion picturephotography, to thereby obtain a talking moving picture, I wish it to beunderstood that I do not desire to be limited or restricted in thisrespect as this particular application has been selected for thepurposes of illustrating the invention involved.

It willthus be apparent that I have provided means which will enablemaking a permanent record not only of plays \but of all talking,singing, or other sound wave producing parts of the plays and enable thereproduction of the same with perfect synchronism inasmuch as they areon the same record or film in proper relation, relative to each other.In the drawing I show diagrammatically at 10 a motion picture camerathrough which the motionpicture film 7 passes intermittently in theusual well known manner. I provide a suitable loop 11 in the passage ofthe film and on one side of the loop I subject the film to the soundcontrolled light rays, the sound for controlling which is produced bythe actors, musicians, or the like, wh1ch are being photographed. Theloop which is provided between the sound recording devices and thecamera or light recording devices is to enable the film 7 to passcontinuously by the lens 3 as distinguished from the intermittent feedof the film past the camera aperture 3 for the obvious reason ofmaintaining the sound record as a continuous record. The relative speedof travel of the film 7 past the sound lens 3 and past the cameraaperture 3 can easily be/ regulated in any well known manner, such as atpresent employed in the motion picture photography art for making andmaintaining speed loops, it being understood that a similar loop ismaintained in the film when a reproduction of the record thereon isobtained.

Many modificationsand changes in details will occur to those skilled inthe art without departing from the spirit and scope description and theillustrations used in connection therewith regarded in the illustrativesense rather than in a limiting sense.

Having now described and illustrated my invention and having set forthand shown a structure. embodying the principles thereof, what I claim asnew and useful and of my own invention, and desire to secure by LettersPatent is 1. The vcombination with an alternating current lamp, 1 cansfor continuously supplying an alternating current to said lamp theperiodicity of which is above the audible limits to effectively maintainsaid lamp a constant source of light, and sound controlled means forvarying said current.

2. The combination with an alternating current lamp, means forcontinuously supplying an alternating current to said lamp theperiodicity of wh1ch is above the audible limits to effectively maintainsaid lamp a constant source'of light, and means for va-v rying thealternating currentso supplied by and in accordance with soundcontrolled alternating currents the periodicity of which is within theaudible limits.

3. The combination with an alternating current lamp, an oscillion forsupplying high frequency oscillations to said lamp to effectivelymaintain said lamp a constant source of light, and sound controlledmeans for modulating said high frequency oscillations.

4. The combination with an alternatin current lamp, an oscillion forsupplying high frequency oscillations to said lamp to effectivelymaintain said lamp a constant source of light, and means for modulatingsaid high frequency oscillations by and in accordance with sound wavesto produce corresponding modulation in thelight emitted bylsaid lamp.

5. cans for photographically recording the sound Waves, comprising anelectrically lighted lamp, means for constantly supplying high frequencyoscillating current to sand lamp to light the same, means forcontrolling said lamp by and in accordance with sound waves, and meansfor directing the light from said lamp to a sensitized element.

6. Means for photographically recording the sound waves, comprising anelectrically lighted lamp, means for constantly supply-- ing highfrequency oscillating current to said lamp to light the same, means forcontrolling said lamp by and in accordance with low frequency currents,and means for directing light rays from said lamp to a sensitizedelement.

minous gas discharge device, means for con stantly maintainingsaid'device efiectivel luminous, and means for varying the luminosity ofsaid device by and in' accordance with sound waves, and means fordirecting the light from'said device to a sensitized element.

8. Means-"for photographically recording sound waves comprising anenclosed luminous gas discharge device, means for constantly maintainingsaid device cfiectively luminous, and means for varying the luminosityof said device by telephone currents, and means for directing 'the lightfrom said device to a sensitized element.

9. The method of photographically recording sound which comprises varyinthe luminosity of an effectively constantl Eminous enclosed gasdischarge device hy in accordance with sound waves.

10. The method of photographically recording' sound which comprisesvarying the luminosity of an efi'ectively constantly luminous enclosedgas discharge device by and and in accordance with telephonic currents.-

In testimony whereof I have hereunto set my hand on this 3d day ofNovember,

LEE DE FOREST.

